Frictionizing composition

ABSTRACT

There is disclosed a frictionizing composition for imparting long-term anti-slip properties to the surface of a paper product comprising an aqueous sol of colloidal silica, glycerin, and at least one agent selected from the group consisting of N-methyl pyrrolidone, N,N-dimethyl acetoacetamide, urea, sorbitol, fructose and dextrose. The composition remains fluid, even after prolonged exposure to drying conditions, and thus is readily dispersible in water for easy cleanup of residue from apparatus and the work environment.

This application is a continuation of my application Ser. No. 08/265,449entitled “Frictionizing Composition” filed Jun. 24, 1994 now U.S. Pat.No. 5,569,318.

BACKGROUND OF THE INVENTION

This invention relates to a composition for imparting anti-slipproperties to the surface of a paper product.

During the manufacture of paper bags and boxes the surface of the paperis typically treated with a frictionizing agent to enhance the anti-slipproperties of the surface of the finished product. The frictionizingagent increases resistance to slip and thus makes stacks of the finishedbags or boxes more stable.

Compositions of colloidal silica are used as frictionizing agents in thepaper industry to impart anti-slip properties to cellulose-based paperand fabricated wood products. The compositions are typically applied toa moving web using spray equipment or contact application equipment suchas transfer rollers or sponges. Such methods tend to deposit thecomposition not only on the paper or wood surface as intended, but alsoas a residue in the immediate work area and on the applicationequipment. Conventional colloidal silica anti-slip compositions dry to ahard cementitious residue which cannot be redispersed in water. Thecementitious residue thus tends to build up on the work area andequipment surfaces, which permits silica chip formation and theformation of silica dust on high speed paper rewind operations. Thesilica particles contribute to equipment wear, and high levels of silicadust are a health hazard for workers. In addition, since the temperaturein the environment of a moving web is typically about 120° F., whenconventional colloidal silica compositions are spray-applied, they tendto dry during application and build up on the spray tip, eventuallycausing the tip to plug.

Various colloidal silica compositions for enhancing surface friction orimparting anti-slip properties to paper surfaces have been disclosed inU.S. Pat. Nos. 4,980,024, 3,860,431, 3,711,416 and 4,452,723. Howeverthere is still a need for a frictionizing composition that impartslong-term anti-slip properties to paper surfaces, which is easy toapply, and the residue of which is readily removable.

SUMMARY OF THE INVENTION

The present invention comprises an improved frictionizing compositionfor imparting anti-slip properties to the surface of paper on which itis applied. The frictionizing composition comprises an aqueous sol ofcolloidal silica, glycerin and at least one agent selected from thegroup consisting of N-methyl pyrrolidone (NMP), N,N-dimethylacetoacetamide (DMAA), urea, sorbitol, fructose and dextrose. Surfacescoated with the frictionizing composition retain their anti-slipproperties for an extended period of time. The frictionizing compositionremains fluid, or retains the ability to flow, when exposed to dryingconditions even for extended periods of time, and remains dispersible inwater so that a residue of the composition can easily be removed withwater.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The composition is prepared in any convenient manner, for example, bymixing together in water the glycerine, and the selected agent oragents, and adding the silica solids to the mixture. The silica solidsare preferably added in the form of a sodium-, potassium- orammonia-stabilized aqueous sol of colloidal silica having a pH between 8and 10.3, and a particle size between 10 and 150 nanometers. A preferredsilica sol is a sodium-stabilized silica sol having a pH between 9 and10 and a particle size of about 100 nanometers. Such a sol iscommercially available as “NYACOL 9950” from Nyacol Products Inc. ofAshland, Mass., which is described as a sodium-stabilized aqueousdispersion of colloidal silica at 50 wt % concentration having a pH of9.5 and a particle size of 100 nanometers.

The glycerine and other agents are industrial grade or better. Apreferred source of NMP is the Arco Chemical Co. of Newtown Square, Pa.An acceptable source of fructose is high fructose corn syrup.

The composition may be diluted up to 80% prior to application by the enduser. When the composition is used in hard water environments,tetrasodium EDTA may be added to the composition as a complexing agentfor metal ions such as calcium and magnesium. A preferred EDTAcomplexing agent is “VERSENE 100” available from the Dow Chemical Co. ofMidland, Mich., which is preferably added in amounts less than 0.6 wt %.Similarly, a biocide may be added to the composition as a preservativeto extend its shelf life. A preferred biocide is “KATHON LX” 1.5%biocide commercially available from Rohm and Haas of Philadelphia, Pa.The complexing agent and the biocide do not affect the frictionizing orfluid viscosity character of the composition.

Representative compositions where the selected agent is sorbitol are setforth below.

Composition (wt %) Ingredients 1 2 3 silica solids 12 20 20 glycerin 1012 10 sorbitol 6 5  6 tetrasodium EDTA 0.17 0.17 — biocide 0.1 0.1 —water 71.73 62.73 64

Representative compositions where the selected agent is NMP are setforth below.

Composition (wt %) Ingredients 5 6 7 8 silica solids 20 20 20 20glycerine 12 16.15 15.3 13.6 NMP 5 .85 1.7 3.4 water 63 63 63 63

Representative compositions where the selected agent is DMAA are setforth below.

Composition (wt %) Ingredients 9 10 11 12 13 silica solids 20 20 20 2020 glycerine 16.5 16 15.5 15 14 DMAA 0.5 1 1.5 2 3 water 63 63 63 63 63

Representative compositions where the selected agent is urea are setforth below.

Composition (wt %) Ingredients 14 15 16 17 18 silica solids 20 20 20 2020 glycerine 16 15 14 13 12 urea 1 2 3 4 5 water 63 63 63 63 63

Representative compositions where the selected ants are sorbitol and NMPare set forth below.

Composition (wt %) Ingredients 19 20 21 22 34 24 25 silica solids 20 2020 20 20 20 20 glycerine 9 8 7 6 5 8.5 6.8 sorbitol 7 7 7 7 7 5.5 8.5NMP 1 2 3 4 5 3 1.7 water 63 63 63 63 63 63 63

Representative compositions having various combinations of two selectedagents are set forth below.

Composition (wt %) Ingredients 26 27 28 silica solids 20 20 20 glycerine 8  8  7 fructose 10 —  5 NMP  2  2 — dextrose — 10 — urea — —  6sorbitol — —  6

The frictionizing composition of the present invention imparts anti-slipproperties to a paper surface as measured by a slide angle test, and thecomposition is easily redispersed in water for easy cleanup of anycomposition deposited as a residue, for example, as over-spray, in thework environment, because the composition has a measurable viscosityeven after prolonged exposure to drying conditions. This propertycontributes to the ability of the frictionizing composition to remaineffective in imparting anti-slip properties to the paper surface duringthe processing of the paper to the finished product.

It is noted that when a colloidal silica composition is applied to apaper surface, it must be sufficiently dry to give a positive result ina standard test for its presence using a lactone dye indicator known inthe industry. In other words, a freshly applied, still wet applicationof a colloidal silica composition will not give a positive result in astandard lactone test for its presence. Although the frictionizingcomposition of the present invention does not dry to a hard residue onwork area surfaces, it does dry on the surface on which it is applied,due to interaction with the surface, to give a positive result in astandard lactone test for its presence.

Slide angle tests were performed to ascertain the effectiveness of thecomposition of the present invention. The apparatus used was acoefficient of friction angle tester model 32-35, available from TestingMachines, Inc. of Ammityville, N.Y., using the TAPPI method T-815SU-72.The slide angle test is performed by securing to a horizontal supportone of a pair of sheets whose surfaces will be tested, with the testsurface facing up. The second sheet is placed on the first sheet withthe test surface facing down. A weight is placed on the second sheet.The support pivots at a first end as the second end of the support israised at the prescribed rate. When the weighted sheet begins to slide,the incline angle, or slide angle, is determined. This slide angle isconsidered to be a measure of the anti-slip properties of the surface ofthe sheet.

EXAMPLE 1

Composition 1, disclosed above, was diluted one part composition to twoparts water and applied by spraying at 30 psi and in a 7″-wide patternto 42# white liner box blanks traveling on a web at 600 ft/min. Theslide angle of the treated surface was measured as noted above. Theslide angle of an untreated liner was also measured. The results arepresented below in Table 1.

TABLE 1 Slide Angle, Average of 3 Composition Treated Untreated 1 38°28°

EXAMPLE 2

Under the same conditions described above in Example 1, composition 1was applied to a 42# Kraft liner and the slide angle of the treatedsurface was measured. The slide angle of an untreated liner was alsomeasured. The results are presented in Table 2.

TABLE 2 Slide Angle, Average of 3 Composition Treated Untreated 1 37°20°

All compositions of the present invention, when similarly applied,provide similar slide angles on the surfaces to which they are applied,and the so-treated surfaces retain their original slide angle valueseven after undergoing conveyor line processing.

The composition of the present invention retains a measurable viscosityeven when exposed to the atmosphere for long periods of time. Becausethe composition does not solidify, or form a hard, cementitious deposit,it remains readily dispersible in water. The composition is thus easy toapply, and because of its especially fluid nature, little silica-dustingoccurs.

The viscosity of the frictionizing composition of the present inventionwas determined over a period of time by the following test. A 10 mlaliquot of the composition was placed in each of three 50 ml planchettesand allowed to dry at room temperature for periods of one week or 10days, two weeks or 19 days, and five or six weeks. At the end of eachtest period the planchettes were tipped at an angle of 30-45° todetermine flow characteristics. In all cases, the composition retained areasonably high degree of flowability, as evidenced by its flow first tothe low side of the planchette, then to the other side of the planchetteafter tipping the planchette 30-45° in the opposite direction. In orderto measure relative viscosity, the time required for the composition toflow from the high to the lower side of the planchette was measured, andwas designated as “flow time.” The measured flow times are set out inTable 3.

TABLE 3 Flow Time (in Seconds) Composition 7 days/10 days 2 weeks/19days 5 weeks/6 weeks 3 9 — 6 — 22 — 4 — 9 — 10 — 10 6 4 — 2 — 4 — 7 3 —2 — 3 — 8 2.5 — 2 — 3 — 9 — 2 — 3 — 3 10 — 1.5 — 3 — 2 11 — 1.5 — 3 — 212 — 1.5 — 2.5 — 2 13 — 1.5 — 2 — 1.5 14 — 2.5 — 4 — 2 15 — 2 — 3 — 2 16— 2 — 3 — 2 17 — 2 — 2.5 — 2 18 — 2 — 2.5 — 2 19 — 6 — 11 — 12 20 — 6 —10 — 19 21 — 8 — 14 — 28 22 — 6 — 10 — 32 23 — 6 — 11 — 45 24 — 4 — 10 —26 25 10 — 7 — 25 — 26 13 — 7 — 30 — 27 9 — 5 — 30 — 28 2 — 2 — 3 —

What is claimed is:
 1. A frictionizing composition comprising: (a) anaqueous sol of colloidal silica; (b) glycerin; and (c) sorbitol.
 2. Africtionizing composition comprising: (a) an aqueous sol of colloidalsilica; (b) glycerin; (c) urea; and (d) sorbitol.
 3. A non-skid surfacecomposition comprising an aqueous suspension of glycerine, colloidalsilica and sorbitol, wherein the ratio of colloidal silica to glycerineis about 1.2:1 to 4:1.
 4. A method of increasing the coefficient offriction of the surface of a cellulosic substrate comprising the stepsof: (a) applying a non-skid surface composition comprising an aqueoussuspension of glycerine, sorbitol, and colloidal silica, wherein theratio of said colloidal silica to glycerine is between about 1.2:1 to4:1, to the surface of said substrate, and (b) drying the surface ofsaid substrate.
 5. The non-skid surface composition according to claim3, wherein the ratio is between about 1.2:1 to 2:1.
 6. The non-skidsurface composition according to claim 3, wherein the colloidal silicahas a particle size between 10 and 150 nm.
 7. The non-skid surfacecomposition according to claim 3, wherein the colloidal silica ispresent in an amount of 12-20% by weight of the composition.
 8. Thenon-skid surface composition according to claim 3, wherein the glycerineis present in an amount of 5-10% by weight of the composition.
 9. Thenon-skid surface composition according to claim 3, further comprisingfructose or dextrose.